In the forming of vehicle tires it is desirable that the tire side wall be free of any radially projected rubber pins, impressions or other surface irregularities. The forming of the pins is usually the result of the tire band, in the final forming operation, being forced into the air release passages which have terminal ends open to the inner surface of the tire forming cavity of the molding machine. For economical purposes, the pins are not removed and thus give to the tire an unfinished appearance. The forming of cavities or depressions in the tire wall not only deface the tire but provide pockets for road dirt accumulations. In any event, where vehicles are on display, the pins or side wall blemishes detract not only from the overall appearance of the tire but also from the overall appearance of the vehicle.
Attempts to avoid surface irregularities on the tire side wall have been made particularly with regard to avoiding the necessity and resultant expense of removing the rubber pins from the finished tire. In the case of side wall depressions or the like surface irregularities, such are left untouched and thus permanently deface the finished tire. One attempt to eliminate the rubber pins is shown in British Pat. No. 922,788, issued Apr. 3, 1963, wherein there is disclosed a one piece valve body extended within a mold aperture and movable by an expanding tire band into an aperture closing position. The valve is not movable to a full open position and is apparently limited in operation to horizontally extended apertures so that the depressions formed in the tire tread appear as part of the tread.
In U.S. Pat. No. 4,021,168, bent nails having one or more washers positioned between the nail head and the face of the mold and inserted into the vents or passages of the tire mold. A washer nail prevents rubber protrusions from forming in the vents during molding but allows the escape of air. It is also apparent that the nail head and washer assembly forms depressions over the entire tread and tire side wall surfaces.
The tire forming method of U.S. Pat. No. 3,842,150 provides for the forming of a tire having smooth side walls which are free of any radially protruding rubber pins or surface irregularities. The release of air from the tire cavity through passages, having terminal ends open to the tire cavity side wall, is controlled by valves which are actuated in response to the selective application thereon of air under pressure and sub-atmospheric air. Although this method performs satisfactorily, appreciable time and resultant expense are involved in the forming of the various valve structures and air passages, and the control system for controlling the flow of air through the passages to actuate the valves in synchronisms with the tire forming operation.